This research will assess the ability of the Premack Principle (Premack, 1959) and the Response Deprivation Hypothesis (Timberlake & Allison, 1974) to predict increases of instrumental responding in reinforcement schedules established for severely and profoundly retarded persons. These tests will take place in schedules where a higher-probability behavior serves as the contingent response, a lower-probability behavior serves as the contingent response, the variable of response deprivation is present in the schedule, the variable of response deprivation is absent from the schedule, and, in schedules where there is no contingent relationship between the instrumental and contingent responses. Additionally, the predictions these hypotheses make concerning the necessary conditions for reversibility of reinforcement will be evaluated. Recent work with rats and college students has provided support for the Response Deprivation Hypothesis in these types of schedules. The first five experiments will be conducted in a laboratory setting with the participants engaging in manipulatory behaviors. These tests are intended to provide a scientific evaluation of the hypotheses. The final three experiments will be conducted in applied settings and will attempt to provide support for the idea that the results of prior studies suggesting support for the Premack Principle in such situations merely reflect the effects of response deprivation. These latter studies will also evaluate the protential advantages of the Response Deprivation Hypothesis as a guide for establishing effective reinforcement schedules for the severely and profoundly retarded in applied settings.